METHOD FOR CONTROLLING A WIND POWER INSTALLATION

Abstract

Provided is a method for controlling a wind power installation. The wind power installation includes a generator for generating a generator current with one or more generator current phases, and an active rectifier for rectifying and controlling the generator current. For each generator current phase the rectifier has a plurality of controllable sub-rectifiers. Each controllable sub-rectifier is characterized by a partial inductance, each controllable sub-rectifier controls a partial current of the generator current phase and each generator current phase forms a summation current as a sum of all the partial currents of the relevant generator current phase. The active rectifier is controlled so that for each generator current phase the summation current is detected and each controllable sub-rectifier of the relevant current phase controls the partial current thereof depending on the detected summation current.

Claims

1. A method for controlling a wind power installation, comprising: generating, by a generator, current having a plurality of phases; rectifying and controlling, by an active rectifier, the current, wherein for each phase of the plurality of phases the active rectifier includes: a plurality of controllable sub-rectifiers, each controllable sub-rectifier of the plurality of controllable sub-rectifiers is associated with a partial inductance; controlling, by each controllable sub-rectifier of the plurality of controllable sub-rectifiers, a respective partial current of a plurality of partial currents of the phase; summing the plurality of partial currents of each phase of the plurality of phases to produce a respective summation current of a plurality of summation currents; detecting, for each phase of the plurality of phases, the summation current of the plurality of summation currents; and controlling the active rectifier based on the plurality of summation currents of the plurality of phases, the controlling the active rectifier including: controlling, by each controllable sub-rectifier of the plurality of controllable sub-rectifiers, the respective partial current based on the summation current of the phase associated with controllable sub-rectifier.

2. The method as claimed in claim 1, comprising: operating the active rectifier according to a hysteresis method, wherein: a tolerance band having an upper band limit and a lower band limit is set for each summation current of the plurality of summation currents, and each controllable sub-rectifier of the plurality of controllable sub-rectifiers controls the respective partial current depending on whether the summation current reaches the upper band limit or lower band limit.

3. The method as claimed in claim 2, wherein: each controllable sub-rectifier of the plurality of controllable sub-rectifiers has at least one switch and is configured to control the respective partial current by switching the at least one switch, and the switching of the at least one switch is controlled depending on whether the summation current reaches the upper band limit or lower band limit.

4. The method as claimed in claim 1, wherein: each controllable sub-rectifier of the plurality of controllable sub-rectifiers is associated with a delay time, and each controllable sub-rectifier of the plurality of controllable sub-rectifiers controls the respective partial current depending on the delay time.

5. The method as claimed in claim 4, wherein each controllable sub-rectifier of the plurality of controllable sub-rectifiers switches the at least one switch after the respective summation current has reached an upper band limit or lower band limit and the delay time has elapsed.

6. The method as claimed in claim 4, wherein the delay time is determined depending on the partial inductance of the controllable sub-rectifier.

7. The method as claimed in claim 1, comprising: detecting a respective deviation of each partial current of the plurality of partial currents from an average partial current; and controlling the respective controllable sub-rectifier depending on the respective deviation.

8. The method as claimed in claim 7, wherein controlling the respective controllable sub-rectifier depending on the respective deviation includes determining a delay time depending on the respective deviation.

9. The method as claimed in claim 1, comprising: determining a dynamic correlation between a switching of a controllable sub-rectifier and a resulting partial current based on a sub-rectifier voltage, a current profile associated with the sub-rectifier voltage and a detected generator inductance of the generator; and controlling the controllable sub-rectifier depending on the dynamic correlation and the summation current.

10. The method as claimed in claim 9, comprising: determining a delay time depending on the dynamic correlation; and controlling, by the controllable sub-rectifier, the switching depending on the delay time.

11. The method as claimed in claim 1, wherein: a central controller detects the respective summation current, generates a plurality of control signals for the plurality of controllable sub-rectifiers and transmits the plurality of control signals to the plurality of controllable sub-rectifiers to control the plurality of controllable sub-rectifiers.

12. The method as claimed in claim 11, wherein: switching time adjustments for the plurality of controllable sub-rectifiers are determined and transmitted to the plurality of controllable sub-rectifiers by the central controller, and propagation times of the transmission the plurality of control signals to the plurality of controllable sub-rectifier are determined and accounted for in the determination of the switching time adjustments.

13. The method as claimed in claim 12, wherein delay times of the plurality of controllable sub-rectifiers and/or the propagation times are stored using a control protocol and used to control the plurality of controllable sub-rectifiers.

14. The method as claimed in claim 1, comprising: performing, by each controllable sub-rectifier of the plurality of controllable sub-rectifiers, switching in order to generate a voltage pulse, performing the switching include: triggering the switching to trigger a voltage pulse; and terminating the switching to terminate the voltage pulse, wherein: a time interval between the triggering of the switching and the terminating of the switching indicates a pulse width of the voltage pulse, and different switching time adjustments and different and variable delay times are provided for the triggering of the switching and the terminating of the switching in order to control the pulse width.

15. The method as claimed in claim 1, wherein: three sub-rectifier arrangements including a sub-rectifier arrangement of a first current phase, a sub-rectifier arrangement of a second phase and a sub-rectifier arrangement of a third current phase and a network-based sub-inverter arrangement form a back-to-back sub-converter, each back-to-back sub-converter has a common DC link to which the sub-rectifiers of a respective sub-rectifier arrangement rectify and from which the sub-inverter arrangement inverts, and DC links of a plurality of back-to-back sub-converters are coupled to permit circulating currents via the DC links.

16. A wind power installation, comprising: a generator configured to generate current having one or more phases; an active rectifier configured to rectify and control the current, wherein for each phase of the one or more phases, the rectifier includes: a plurality of controllable sub-rectifiers, each controllable sub-rectifier of the plurality of controllable sub-rectifiers being characterized by a partial inductance, and each controllable sub-rectifier of the plurality of controllable sub-rectifiers being configured to: control a partial current of a plurality of partial currents of a respective phase of the one or more phases, each phase forming a summation current as a sum of the plurality of partial currents of the phase; and a controller configured to: control the active rectifier; detect the summation current for each phase of the one or more phases; and control each controllable sub-rectifier of a respective phase depending on the summation current for the respective phase.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0080] The invention will now be discussed in more detail below by way of example on the basis of exemplary embodiments with reference to the accompanying figures.

[0081] FIG. 1 shows a perspective illustration of a wind power installation.

[0082] FIG. 2 schematically shows a rectifier of a phase by way of example with three sub-rectifiers.

[0083] FIG. 3 schematically shows a structure for controlling a plurality of sub-rectifiers.

DETAILED DESCRIPTION

[0084] FIG. 1 shows a schematic illustration of a wind power installation. The wind power installation 100 has a tower 102 and a nacelle 104 on the tower 102. An aerodynamic rotor 106 having three rotor blades 108 and having a spinner 110 is provided on the nacelle 104. During the operation of the wind power installation, the aerodynamic rotor 106 is set in rotational motion by the wind and thereby also rotates an electrodynamic rotor or armature of a generator, which is coupled directly or indirectly to the aerodynamic rotor 106. The electric generator is arranged in the nacelle 104 and generates electrical energy. The pitch angles of the rotor blades 108 can be varied by pitch motors at the rotor blade roots 109 of the respective rotor blades 108.

[0085] The wind power installation 100 in this case has an electric generator 101, which is indicated in the nacelle 104. Electrical power can be generated by means of the generator 101. An infeed unit 105, which can be designed, in particular, as an inverter, is provided to feed in electrical power. It is thus possible to generate a three-phase infeed current and/or a three-phase infeed voltage according to amplitude, frequency and phase, for infeed at a network connection point PCC. This can be effected directly or else jointly with further wind power installations in a wind farm. An installation control system (e.g., controller) 103 is provided for controlling the wind power installation 100 and also the infeed unit 105. The installation control system 103 can also acquire predefined values from an external source, in particular from a central farm computer. An active rectifier, which may be part of the infeed unit 105, is connected to the generator 101.

[0086] FIG. 2 illustrates a sub-rectifier arrangement 200 of a phase, which comprises a plurality of sub-rectifiers 201-203. A plurality of such sub-rectifier arrangements 200 of a phase can then together form an overall active rectifier, which is then used overall to rectify and control the generator current of a generator of a wind power installation. In this case, however, only one sub-rectifier arrangement of a phase is considered. Corresponding sub-rectifier arrangements are provided for further phases.

[0087] The sub-rectifier arrangement 200 of a phase thus has three sub-rectifiers 201-203. The third sub-rectifier 203 as sub-rectifier N can also be representative of all further sub-rectifiers that overall form the sub-rectifier arrangement 200 of a phase.

[0088] In FIG. 2, the basic structure of the design of said sub-rectifier arrangement 200 of a phase from a plurality of sub-rectifiers 201-203 is intended to be explained, namely on the generator side. Each sub-rectifier 201-203 may have a DC output 211-213. Each sub-rectifier 201-203 may also be formed as part of a sub-converter arrangement. In this case, a DC link would be provided internally and instead of the DC output 211-213 an AC voltage output would be provided.

[0089] Each sub-rectifier 201-203 has a generator-side output 221-223. Furthermore, each sub-rectifier 201-203 has a partial inductance 231-233. Each partial inductance 231-233 is symbolized in FIG. 2 as a component connected to the generator-side output 221-223. However, it is also representative of inductances that can result for example due to the feed line or also takes this into account.

[0090] A control part 241-243 is provided to control each sub-rectifier 201-203. The control part can receive control signals and thus control semiconductor switches of the sub-rectifier in order thereby to generate a pulsed voltage signal that is intended to lead to a modulated sinusoidal current A switching voltage V.sub.S1, V.sub.S2 or V.sub.SN is produced directly at the generator-side output of the inverter, said switching voltage changing between a positive value, negative value and the value of zero substantially depending on the corresponding switch positions. A generator-side voltage V.sub.1, V.sub.2 and V.sub.N and a generator-side current i.sub.1, i.sub.2 and i.sub.N is produced at the generator-side output of the partial inductance 231, 232 or 233. Each of said generator-side currents i.sub.1, i.sub.2 and i.sub.N forms a partial current of the generator current of the relevant phase. Said generator current of the relevant phase thus forms the summation current of said generator current phase. This is shown in FIG. 2 as summation current is and flows through a generator inductance 234. In this case, in the schematic illustration of FIG. 2, which can also be regarded as an equivalent circuit diagram, the generator 250 is taken into account as voltage source with the voltage VG.

[0091] The generator-side voltages V.sub.1, V.sub.2 and V.sub.N and the partial currents i.sub.1, i.sub.2 and i.sub.N can be detected at a detection point (e.g., ammeter, voltmeter or multimeter) 261, 262 and 263, respectively, and transmitted to the respective control part (e.g., controller) 241-243 or the respective control part 241-243 detects the respective voltage and the respective partial current at the detection point. The control parts 241-243 can then transmit the values detected in this way to a central control system and/or to a control unit.

[0092] FIG. 3 schematically illustrates in a simplifying manner a possible control concept.

[0093] In this case, FIG. 3 uses a sub-rectifier arrangement 200 of a phase, as has been explained in FIG. 2. However, for the sake of clarity, of the sub-rectifier arrangement 200 of a phase, FIG. 3 illustrates only a part of the one illustrated in FIG. 2. In particular, the control parts 241-243 for each sub-rectifier 201-203 are illustrated. These control parts 241-243 detect the generator-side voltages V.sub.1, V.sub.2 and V.sub.N and the partial currents i.sub.1, i.sub.2 and i.sub.N. These values are passed to a central control system (e.g., central controller) 300, which in this case is delimited schematically by a dashed border.

[0094] Of these values, in each case the partial currents i.sub.1, i.sub.2-i.sub.N are summed in a summing element (e.g., summing node) 302 and then result in the summation current i.sub.Σ. This summation current i.sub.Σ may correspond to the summation current is in FIG. 2 or should ideally correspond thereto. However, the summation current is in FIG. 2 in this respect denotes the actual summation current, whereas the summation current i.sub.Σ in FIG. 3 is a computation variable, namely the sum of the partial currents i.sub.1, i.sub.2-i.sub.N. Where measurement errors or measurement inaccuracies are permitted to be disregarded, the calculated summation current i.sub.Σ corresponds to the actual summation current is in FIG. 2.

[0095] In any case, said calculated summation current i.sub.Σ is input into a modulation block 304. The modulation block 304 uses a tolerance band method in order to modulate a setpoint current i.sub.setpoint. For this purpose, a tolerance band is placed around said prescribed current i.sub.setpoint, which is prescribed according to magnitude, frequency and phase, and thus is prescribed as a sinusoidal current Depending on whether the summation current i.sub.Σ contacts an upper or lower tolerance limit, a switching signal between 0 and 1, or between 0 and −1, is output. This additionally depends on whether the current that is to be generated is currently positive or negative, to put it clearly.

[0096] The result of the modulation block, that is to say of the tolerance band method executed in the modulation block 304, is thus a switching signal that is basically provided for each sub-rectifier. The sub-rectifier is intended to switch the switching voltage V.sub.S1, V.sub.S2 and V.sub.SN, respectively, according to the switching signal, namely to the negative value, the positive value or to zero.

[0097] Said switching signal that is output by the modulation block 304 can thus switch the switch position in each sub-rectifier 201, 202 or 203. If any circulating currents arise, which for example influence the partial current I1 and the partial current I2, however, this has no effect on the switching signal that is generated by the tolerance band method in the modulation block 304.

[0098] As a result, an important target can already be achieved, namely the generation of the summation current by way of parallel-connected sub-rectifiers substantially independently of circulating currents. Furthermore, however, it is proposed to additionally take into account time differences between the individual sub-rectifiers 201-203. Although such consideration can be carried out centrally in a common computation block, for example, this is individually illustrated in FIG. 3 for each sub-rectifier 201-203 for the purposes of illustration. However, the mode of operation explained below is the same for all sub-rectifiers 201-203 in principle. In this respect, this is explained below for the sub-rectifier 201.

[0099] The sub-rectifier 201, which in this respect can also be referred to as the first sub-rectifier, transmits the generator-side voltage V.sub.1 and the partial current i.sub.1 thereof to the central control system and these values are also given here to a first propagation time detection block 311. In this respect, a propagation time is detected in the propagation time detection block and a switching time adjustment is determined in a manner depending thereon. The detected switching time adjustment is transferred to the adjustment block 321. The adjustment block 321 essentially delays the switching signal S. The result is an adjusted switching signal S.sub.1. The adjusted switching signal S.sub.1 is furthermore a switching signal that can have the values 1, 0 or −1, which can also be encrypted in another manner, however. However, the adjusted switching signal S.sub.1 is delayed with respect to the unchanged switching signal S.

[0100] The propagation time detection block 311 also receives this adjusted switching signal S.sub.1 and the generator-side voltage V.sub.1 and the partial current i.sub.1 of the first sub-rectifier. The propagation time detection block 311 can then recognize when exactly a switching command has been transmitted by taking into account the adjusted switching signal S.sub.1. A switching command can in this respect be one upon which the switching signal changes from 0 to 1 or back or from 0 to −1 or back. This time is then known precisely in the propagation time detection block 311 and this can be compared with the resulting result of the generator-side voltage V.sub.1 and partial current i.sub.1 generated by the first inverter 201. It can then thus be recognized which signal results precisely through this adjusted switching signal. Particularly the temporal behavior of the resulting signals is taken into account here but so is an amplitude or an amplitude profile. In this case, consideration is given to the fact that also only one of the two signals, that is to say only the voltage or only the partial current, are taken into account.

[0101] Furthermore, the propagation time detection block 311 takes into account the unchanged switching signal S. From this, it is possible to derive how the overall desired signal should appear.

[0102] Furthermore or as an alternative, an average value of the partial currents i.sub.1, i.sub.2 and i.sub.N can also be used. In order to calculate this average value, only the calculated summation current i.sub.Σ needs to be divided by the number of sub-rectifiers, that is to say N. This is illustrated by the quotient block 306.

[0103] In this respect, the propagation time detection block 311 calculates time delays for the switching time adjustment by which the switching signal S is adjusted in order to obtain the adjusted switching signal S.sub.1. These time delays can in this case be different for a rising edge of 0 to 1 than for the again falling edge from 1 to 0. The same applies to the edge of 0 to −1 and from −1 to 0. As a result, not only can delays be provided in order to compensate for propagation time delays but also pulse widths can be changed. A rising edge for example of 0 to 1 and a falling edge back from 1 to 0 thus result in a voltage pulse with a pulse width. If different delay times are provided for the rising edge of 0 to 1 and the falling edge of 1 to 0, the pulse width can be changed as a result.

[0104] In this context, the procedure involves the propagation time blocks 312 and 313 and the adjustment blocks 322 and 323 in the same manner for the further sub-rectifiers 202 and 203. The result is then that an adjusted switching signal S.sub.1-S.sub.3 is generated for each sub-rectifier 201-203. Each adjusted switching signal S.sub.1-S.sub.3 can in this case take into account different propagation times and also generate pulses with different widths.

[0105] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.